Just drill a hole and pop rivet it, bit of a pain because they used 5/32 diameter rivets and I put it on the top side of the plate so the fan van help keep it cool. When they are on the underside they are suffering from heat rising off the barrel
Did you drill a new hole or just use the existing one it was originally mounted underneath by? Would a 4.0mm or 4.8mm diameter rivet suffice?
PS: I could work it out myself if I was home the moment.